Igniter employing a piezoelectric voltage source



P 25, 1967 B. KOONTZ 3,344,314

IGNITER EMPLOYING A PIEZOELECTRIC VOLTAGE SOURCE Filed Aug. 9, 1965 INVENTORQ LAMONT B. KOONTZ fg; M

ATTORNEY United States Patent 3,344,314 IGNITER EMPLOYING A PIEZOELECTRIC VOLTAGE SOURCE Lamont B. Koontz, Edina, Minn., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed Aug. 9, 1965, Ser. No. 478,134 6 Claims. (Cl. 317-81) The present invention is directed to a piezoelectric voltage source for ignition purposes. More particularly, it is directed to a piezoelectric voltage source wherein the piezoelectric crystal or element is normally in a stressed condition and the voltage is generated during a release and reapplication of the stress on the crystal.

Broadly, the present invention accomplishes its purposes by using a spring biased anvil member to prestress a piezoelectric element. A hammer member is utilized to strike the anvil in a direction so as to relieve the pressure on the piezoelectric element. The force utilized in striking the anvil member is sufficient to relieve most of the stress on the crystal, but does not entirely remove all of the stress. One advantage of such an arrangement is that the crystal is continuously under compressional load where its strength is greatest thereby increasing crystal or element life over the striking mode of operation. Thus, this invention represents an improvement over that of application Serial No. 363,694, filed Apr. 30, 1964, now Patent No. 3,307,053, and assigned to the German branch of the assignee of the present application.

The invention will be best understood from a study of the accompanying drawing and specification wherein:

The figure shows an elevation view, with parts broken away, of one form of the invention wherein the energy for relieving the stress is manually produced.

In the drawing, a housing member or frame is generally designated 10 and may be made of any reasonably rigid material such as metal. Located within the housing 10 and attached thereto is a piezoelectric element 11 preferably of a polarized polycrystalline lead zirconate lead titanate ceramic. The piezoelectric element is shown as being mounted on a support member 12 by electrical insulating material which in turn is afiixed to an adjustable threaded member 13. The opposite end of the piezoelectric element 11 is engaged by an anvil member 14 which is movable although held in compression with the piezoelectric element by strong spring 15. In the illustration shown, the piezoelectric element 11 has been metallized on the axis of compression ends thereof to provide electrical connection means for draining off the voltage produced during operation of the voltage source. These metallized end portions are identified 16 and 17 respectively. The largest voltage output will appear when the axis of compression, the axis of polarization, and the axis of the electrodes are aligned. However, it is contemplated that the electrodes can be applied at right angles to the axis of compression, but aligned with the axis of polarization, although the output per unit applied stress change will be somewhat less than in the preferred form. Electrode 17 is grounded by lead 18 to the frame 10, while electrode 16 is connected to a lead 19 which passes through and is supported by electrical insulation 20 in frame 10 and forms one arm of the spark gap arrangement generally indicated as 21. The other side of the spark gap is in electrical contact with frame 10.

A hammer means 22 is provided in the form of a sleeve surrounding piezoelectric element 11. This sleeve member 22 has oppositely disposed extensions 23 which impact anvil member 14 during the unloading portion of the operation. Sleeve member 22 is attached to a pivoted arm member 24 having an upwardly extending arm 25. Arm 24 and hammer 22 are urged counterclockwise about pivot 26 by a relatively strong spring 27 and are urged in a clockwise direction against spring 27 by arm 28 having an abutment portion 29 engageable with the upper end of lever 25. Ann 28 is hinged to handle member 30 by a spring hinge 31 which tends to hold arm 28 in its maximum counterclockwise position or against the flat upper end of member 30. Normally, handle member 30 will be operated by grasping and squeezing 30 toward stationary handle portion 32 of frame 10.

A relatively light spring 33 tends to hold member 30 against an abutment portion 34 of frame 10, in which position arm 28 is in a position to engage arm 25. However, as handle member 30 is forced toward 32, and arm 25 is moved counterclockwise by arm 28, arm 28 tends to move upwardly with regard to 25 because of its resting against the upper fiat end of 30. Thus upon predetermined movement of 30, arm 25 will be rotated counterclockwise against spring 27 and hammer 22 will move accordingly. Upon arm 28 disengaging from 25, spring 27 is able to drive hammer 22 against anvil 14 and momentarily relieve element 11 of most of its compressive stress. This abrupt change in stress causes a voltage to be generated in element 11 that is conducted by the aforementioned leads to spark gap 21 where, upon sparking, a gas cflame, for instance, can be ignited.

Upon releasing member 30, spring 33 returns said handle member to the position shown against abutment 34 and 28 again assumes a latching position with respect to arm 25, this being permitted by spring hinge 31 permitting any necessary clockwise movement for abutment 29 to move up and over arm 25.

In the modification described with regard to the figure, hammer member 22 is indicated as being in contact with and applying counter pressure to anvil member 14. As hammer member 22 is raised, the pressure on the element 11 is increased. This will result in some charge existing between electrodes 16 and 17. For maximum output it is desirable to provide a means of shorting out this charge so that the element will be in a totally uncharged and stressed condition with hammer member 22 out of contact with anvil member 14. This can easily be done by contact between the hammer member 22 and an electrical contact member 35 also connected to electrode 16. Alternately, the charging cycle of unloading the crystal can be performed so slowly that the charge built up by the increase in stress will be internally dissipated. Obviously, other means of dissipation will be readily apparent to one skilled in this art.

While the form of the invention shown utilizes a manually operated device, it will be readily appreciated that the system can be mechanized.

Having described my invention, I claim:

1. A piezoelectric voltage source comprising:

a piezoelectric element having end surfaces defining an axis of compression and including electrical conductor means adapted to connect opposing end surfaces to voltage utilization means,

support means for said crystal including a stationary member engaging one of said end surfaces along said axis of compression and a movable member adjacent the other of said end surfaces,

first spring means biasing said movable member to apply pressure against said element along the axis of compression,

hammer means adapted to impact said movable member to suddenly release at least a portion of the pressure against said element,

second spring means biasing said hammer means toward said movable member,

and actuating means connected to said hammer means to move the same a given distance away from said movable member to store potential energy in said second spring means, whereupon said hammer means is released to strike said movable member to suddenly release at least a major portion of the compression stress of said element.

2. A piezoelectric voltage source in accordance with claim 1 wherein the axis of compression, the axis of polarization, and the conductor means on opposing ends are all in axial alignment.

3. A piezoelectric voltage source in accordance with claim l'wherein the electrical conductor means are connected to a spark gap.

4. A piezoelectric voltage source in accordance with claim 2 wherein the piezoelectric element is in generally cylindrical form having the ends thereof defining an axis of compression and wherein the hammer mean is in generally sleeve form in noncontacting surrounding relationship with said piezoelectric element.

5. A piezoelectric voltage source in accordance with claim 4 wherein the electrical conductor means are connected to a spark gap.

6. A piezoelectric voltage source in accordance with claim 5 wherein a pivotally mounted lever means is connected to said hammer means and to a force applying means to move said hammer means a given distance away from said anvil to store a predetermined quantity of potential energy in said second spring means and wherein there is provided a disengaging means for releasing said hammer means at said predetermined level of potential energy.

References Cited UNITED STATES PATENTS ANTHONY BARTIS, Primary Examiner.

RICHARD M. WOOD, Examiner.

V. Y. MAYEWSKY, Assistant Examiner. 

1. A PIEZOELECTRIC VOLTAGE SOURCE COMPRISING: A PIEZOELECTRIC ELEMENT HAVING END SURFACES DEFINING AN AXIS OF COMPRESSION AND INCLUDING ELECTRICAL CONDUCTOR MEANS ADAPTED TO CONNECT OPPOSING END SURFACES TO VOLTAGE UTILIZATION MEANS, SUPPORT MEANS FOR SAID CRYSTAL INCLUDING A STATIONARY MEMBER ENGAGING ONE OF SAID END SURFACES ALONG SAID AXIS OF COMPRESSION AND A MOVABLE MEMBER ADJACENT THE OTHER OF SAID END SURFACES, FIRST SPRING MEANS BIASING SAID MOVABLE MEMBER TO APPLY PRESSURE AGAINST SAID ELEMENT ALONG THE AXIS OF COMPRESSION, HAMMER MEANS ADAPTED TO IMPACT SAID MOVABLE MEMBER TO SUDDENLY RELEASE AT LEAST A PORTION OF THE PRESSURE AGAINST SAID ELEMENT, SECOND SPRING MEANS BIASING SAID HAMMER MEANS TOWARD SAID MOVABLE MEMBER, AND ACTUATING MEANS CONNECTED TO SAID HAMMER MEANS TO MOVE THE SAME A GIVEN DISTANCE AWAY FROM SAID MOVABLE MEMBER TO STORE POTENTIAL ENERGY IN SAID SECOND SPRING MEANS, WHEREUPON SAID HAMMER MEANS IS RELEASED TO STRIKE SAID MOVABLE MEMBER TO SUDDENLY RELEASE AT LEAST A MAJOR PORTION OF THE COMPRESSION STRESS OF SAID ELEMENT.
 3. A PIEZOELECTRIC VOLTAGE SOURCE IN ACCORDANCE WITH CLAIM 1 WHEREIN THE ELECTRICAL CONDUCTOR MEANS ARE CONNECTED TO A SPARK GAP. 